Direct spectroscopy of the2S1/2−2P1/2and2D3/2−2P1/2transitions and observation of micromotion modulated spectra in trapped40Ca+

We present an experimental scheme to perform spectroscopy on ions and atoms with a lambda-level structure. By rapidly switching lasers between both transitions, we circumvent the complications of both dark resonances and the ac-Stark effect. We demonstrate the scheme on the 2 S 1/2 − 2 P 1/2 and 2 D 3/2 − 2 P 1/2 transitions in 40 Ca + and, within a measurement time of 10 min, extract the centre frequencies of both dipole transitions with a statistical uncertainty on the order of 200 kHz. We also apply this method to directly observe the micromotion modulated fluorescence spectra of both transitions and for the first time measure the dependence of the micromotion modulation index on the trap frequency for both transitions.